A conventional fixing device includes a cylindrical fusing film having an internal space and an inner surface, a heater disposed in the internal space, a nip plate in sliding contact with the inner surface, and a pressure roller that nips the fusing film in cooperation with the nip plate. A sheet carrying a toner image is passed through a nip portion defined between the fusing film and the pressure roller, so that the toner image can be thermally fixed onto the sheet.
The fusing film of the conventional fixing device is made from flexible metal such as stainless steel or nickel, and the nip unit of the conventional fixing device is made from metal such as aluminum, copper, or their alloys.